With the development of consumer electronic products such as mobile phones and electronic compasses, additionally together with conventional products such as motors and brakes, the demand on a magnetoresistive-type sensing device (also referred as magnetoresistive sensing device) is progressively increasing. Especially, a three-dimensional magnetoresistive sensing device is usually used to sense the magnetic field changes of three orthogonal axes (i.e. the X, Y and Z axes). For example, the electronic compass utilizes the three-dimensional magnetoresistive sensing device to precisely measure the earth's magnetic field.
As known, the technology of using a semiconductor manufacturing process to fabricate a two-dimensional planar magnetoresistive sensing device has been well established. However, it is difficult to use a single semiconductor substrate to construct a three-dimensional magnetoresistive sensing device. With the package assembling approach, one planar magnetoresistive sensing chip responsible for measuring the Z-axis magnetic field parallel to the horizontal plane of the substrate should be mounted orthogonally to the other planar magnetoresistive sensing chip responsible for measuring the magnetic field in the X and Y-axis directions in the horizontal plane of the substrate. With alternative approach employing magnetic flux guide, the magnetic field in the Z-axis direction perpendicular to the horizontal plane of the substrate is conducted to the X-Y direction parallel with the horizontal plane of the substrate by a flux concentrator, and then the magnetic field change in the Z-axis direction is measured by an X-Y magnetoresistive sensing device.
From the description above, the conventional device for measuring the magnetic field change in the Z-axis direction has a very complicated structure and high fabricating cost. Moreover, since the process variation of vertical assembling of the chips should be further taken into consideration, the production yield is adversely affected.
For solving the above drawbacks, there is a need of providing an improved magnetoresistive sensing device and a fabricating method thereof. Moreover, the improved magnetoresistive sensing device for measuring the magnetic field change in the Z-axis direction can be merged with other magnetoresistive sensing devices responsible for sensing magnetic field in the X and Y-axis directions to form an integrated three-dimensional magnetoresistive sensing device on a single chip, which is fabricated by a semiconductor manufacturing process.